Bladed rotors for axial flow turbines and similarly bladed fluid flow machines



March 26, 1957 c. GRANTHAM 2,786,646

BLADED ROTORS FOR AXIAL FLOW TURBINE-S AND SIMILARLY BLADED FLUID FLOWMACHINES Flled July 10, 1950 nven for United States Patent-O "ice BLADEDROTORS FOR AXIAL FLOW TURBINES 'AND IMILARLY BLADED FLUID FLOW MA- CHINCyril Grantham, Bagshot, England, assignor to Power Jets (Research andDevelopment) Limited, London, England, a British company ApplicationJuly 10, 1950, Serial No.'172,818

\ Claims priority, application Great Britain August 10, 1949 3 Claims.(Cl. 253-3915) This invention relates to bladed rotors for axial flowturbines and similarly bladed fluid flow machines, to certain featuresof the blades and rotors themselves, and to a method of manufacturingand assembling these elements.

In general, the invention has for its object to provide a method ofmanufacture and form of construction of such a rotor and its componentparts which will lend itself to mass production methods of manufacture.in order to achieve this general object the invention seeks to take intoaccount two main factors; firstly the importance of eliminating as faras possible meticulous machining operations; secondly, the advantagesthat would accrue if the blades could be fabricated from fiat metalsheet or strip stock.

According to the invention a bladed rotor for an axial flow turbine orsimilarly bladed fluid flow machine comprises a rotor body and, disposedperipherally round said body, a plurality of hollow metal blades eachfabricated from uniformly thick sheet material, each blade having aprofiled working portion and, at the radially inner end of said workingportion, a lateral skirt which extends over the peripheral surface ofthe rotor body and is. se-

cured to the corresponding skirt of an adjacent blade.

According further to the invention the rotor body is provided with aplurality of evenly spaced radially upstanding peripheral projectionseach of which is at least partly enclosed by one of the blades, andmeans may be provided for attaching each of the blades to the projectionenclosed thereby.

The blades for a bladed rotor in accordance with the invention arepreferably made in two complementary parts from flat strip or sheetmaterial, each part being cut and pressed to provide the shell for oneface of the blade profile and the two parts being joined (usually rafter assembly) along the leading and trailing edges of the blade as bywelding.

By means of the invention in its broadest aspect each sheet metal blademay be provided with a skirt portion at its radially inner end shaped toconform to the surface of the rotor body, which skirtportion may meetedge to edge the skirt of the next ad jacent bladeand be secured'theretoby,for instance, welding. In this way the entire periphery of the rotorwill be sheathed in a skin of sheet metal which may be arranged withoutdifficulty, to extend radially inwardly over either or both the endfaces of the rotor. If desired it may also be arranged that this skin atleast in some regions shall be spaced from the surface of the rotor bodyto provide a cooling air film between the two parts, although in somecases it may be found preferable to provide good thermal contact betweenthe skin and the body over the maximum possible area. In this way alsothe blades are integrated (independently of any further provision fortheir individual attachment to the rotor) to form a continuous ringwhich is capable of resisting centrifugal loads on each constituentblade and so is effective in contributing to the support of the blades.

2,786,646 P tent d M r- 26, 1. 1

In the practical execution of the invention it is proposed that therotor should be provided with radially upstanding tooth-like projectionswhich are made to conform at least partly to the internal shape of theblades, the latter being mounted so that each encloses a projection andbeing secured thereto, as for example by welding or brazing at a regionradially outward of the inner end of the blade. It will be apparent thatby suitable choice of the radial height of the projections the radiallocation of the region of attachment of a blade withrespect to itsradial height may be made to conform to any desired relation betweenwall thickness and blade stress.

As a further feature, the invention contemplates that the projections onwhich the blades are mounted may be formed to provide air passages forthe flow of cooling air through the blades.

This might be achieved by grooving the external surface of theprojections or by providing suitable internal passages therein or byarranging that a free space will be left within the blade at certainregions such as the leading and trailing edges; or, again, eachprojection may be subdivided transversely to the direction of workingfluid flow past the blade by passages extending across the wholecross-sectional thickness of the projection. In any of these cases theblade may be attached to the projection, as by welding or brazing overan extended time to provide a good thermal connection. It will be notedin this respect that the invention offers the possibility of aparticularly good heat path from the blade to the main rotor body.

According to a further important feature of the invention the rotor andits projections are built up from a series of laminae. The use of arotor of this type (which is not new per se) has the advantage that-theformation of suitably shaped projections to receive the blades isgreatly facilitated, since successive larninaemay be provided withprojections each of which is required to occupy only a small part of theinternal cross section of a blade. The projections on successive laminaemay therefore be differently dimensioned initially, having in mind thedimension of the blade cross-section at the region to be occupied, andthe individual projections can readily be made to conform withsuflicient accuracy to the internal profile of a blade partly by beingpressed 'o'r otherwise worked to shape and partly by effectingappropriate relative angular displacement of successive laminae so thatsuccessive projections are in appropriately staggered relationship. If,as is preferred, the laminate are of sheet metal, manufacture is evenfurther simplified since the projections may be produced by such operations as stamping and pressing. The use of a laminated construction alsolends itself well to the provision of cooling passages between or aroundthe individual projection associated with any one blade, moreparticularly in permitting'a series of transverse-passages to be pr'ovided across the entire internal cross-section" of the blade profile,and in allowing certain parts of the internal cross-sectionof the bladeto be left vacant, which may be done by the simple expedient of omittingthe projections from any desired laminae.

An example of construction of a rotor in accordance with the inventionis illustrated in the accompanying drawings as applied to a laminatedrotor body.

In the drawings Figure 1 is a partial perspective view of a laminatedrotor assembled ready for the mounting of blades thereon; Figure 2 is asimilar view in which the blades are shown partially assembled; andFigure 3 is a view section illustrating a modified type of laminatedblade construction in accordance with the principles of the presentinvention.

As can be seen from the drawings, the rotor body is built up from aseries of laminae 1 (preferably of sheet metal) certain of which areprovided with radially up,- standing projections 2, these projectionshaving been initially dimensioned to suit the width of the part of theblade, profile to'which they are to correspond, andhaving been thenpressed so that their lateral faces conform tothe internal shapeof theblade profile at that part, the laminae composing; the rotor body havingbeen appropriatelyrelatively displaced so that the projection formed bythe aggregation of the individual projections 2 corresponds closely witha portion of the internal shape of the blade profile.

Each=blade ism-adein two parts 3, 4 by pressing suit- .ablyl dimensionedfiat sheets to an appropriate curvature and to provide skirt portions3a, 4a, the parts 3, 4 being the-respective faces ofthe finished bladeand being formed sotthat their longitudinal edges abut to form theleading and trailing edges of the blade. As seen in Figure 2, thesebladeparts are now assembled, one on either side of each projection on therotor body, and welded together down their leading and trailing edgesas. shown at 7. Alternatively the two parts of a blade may be weldedtogether before being assembled on the rotor body, using a jigor former.The latter method'rnay aid the attainmentof accuracy of the blade form.It will be noted that the skirt portions 3a, 4a of successive blades arealso arranged'to abut and these are seam welded together at 7a; whilstthe parts 3 and 4 of the blade are secured, also by welding at 7b, tothe rotor projections.

As will be clearly seen from the drawings the two axially outermostlaminae may be devoid of projections so that a space 8' is formed in theleading and trailing edges of the blade for the passage of cooling air,entry of which may be provided for by a recess 5 in the rotor. .15.;best seen in Figure 3, iris-arranged that there are gaps at 6 betweensuccessive laminae and corresponding; gaps 6:: between successivesections of the blade carrying projections, through which gaps 6, 6acooling air may be supplied from a radially inner region of the rotor.

What I claim is:

1- A bladed rotor for an axial flow turbine or similarly bladed fluidflow machine comprising a plurality of discs with-integrally formedradially extending projections spaced around their peripheries, thediscs being concentrically integrated to form a rotor body having theprojections on successive discs arranged to form groups spacedevenlyaround the periphery of said rotor body, a disc free of projections oneach face of the integrated rotor'body and an open ended hollow bladeextending over each group of projections and overlying a portion a ofthe periphery of the projection-free discs, each hollow blade and atleast one of said projection-free discs eing so spaced as to definetherebetween a gas flow passageway leading to the hollow interior ofsaid blade, each blade having a workingportion and being positively attached to the rotor body solely by attachment to at least someof theprojections of the group over which it extends, only at a, point spacedoutwardly from the inner end of said working portion, and a skirtportionextending from the inner end of said working portion.peripherally of the rotor body to meet the corresponding skirt of anadjacent blade.

2.. A bladedrotortforanaxial flow turbine or similarly bladed fluid flowmachine comprising a plurality of discs with integrally formed radiallyextending projections spaced around their peripheries, the discs beingconcentrically integrated to form a rotor body having the projectionsonsuccessive discs arranged to form groups spaced evenly around theperiphery of said rotor body, a disc free of projections on each faceor" the integrated rotor body and a hollow blade extending over eachgroup of projections and overlying a portion of the periphery of theprojection-free discs, eachhollow blade and said projection-free discsbeing so spaced as to define therebetween gasfiow: passageways leadingto the hollow interior of said blade at each end of the rotor, eachblade having a working portion and being positively attached to therotor body solely'byattachment to at least some of the projections ofthe group over which it extends only at a point spaced outwardly fromthe inner end of said' working portion, and a skirt portion extendingfrom the inner'end of said working portion peripherally of the rotorbody to meet the corresponding skirt of an adjacent blade.

3. A bladedi'rotorfor an axial fiow turbine or similarly'bladedfiuidfiow'machine comprising a generally cylindrical rotor body having radialprojections spaced evenly around its periphery, the rotor body extendingaxially beyondthe projections at each of its ends to provide a portionhaving a projection-free periphery at each end'of the rotor body, anopenended hollow blade extending over each projection and overlying theadjacent area of the projection-free periphery at each end of said body,each hollow blade and at least one of said portions having a projectionfree periphery being so spaced as to define therebetweena gas fiowpassageway leading to the hollow interior of said blade, each bladehaving a working portion and being positively attached to the rotor bodysolely by attachment to the projection over which it extends only at apoint spaced outwardly from the inner end of said working portion, and askirt portion extending from the inner end of said working portionperipherally of the rotor body to meet" the corresponding skirtv of an.adjacent blade.

ReferencesCited in the file of this patent UNITED STATES PATENTS1,363,692 Summer's Dec. 28, 1920 1,516,607 Johanson Nov. 25, 19242,149,510 Darrieus Mar. 7, 1939 2,347,034 Doran Apr. 18, 1944 2,405,190Darling Aug. 6, 1946 2,501,038 Fransson Mar. 21, 1950 2,553,078 Buck May15, 1951 2,618,462 Kane Nov. 18, 1952 FOREIGN PATENTS 16,157' GreatBritain June 4, 1903 141,017 GreatBritain of 1919 235,304 Great BritainJune 12, 1925 576,218: Great Britain; Mar. 25', 1946 614,547Great-Britain Dec. 17, 1948

